I feel that the ambivalence stretches further then just your marriage. I really get a ho hum feeling about life from you. As if you aren't that excited about any of it really...except mothering.
I really want you to start looking inward. Start healing. Start finding your truths. If you do this, if you find what inspires you in life, you will find that your marriage problems are really just a way to deflect your own personal unhappiness. You are looking for something or someone else to blame. It's easiest to find fault and blame with those we love instead of taking responsibility.
I actually think if you do the internal work, that your marriage could not only survive, but THRIVE. I really feel this.
It's time for you to learn about you and to love yourself. That's the key to this equation.